1. Field of the Invention
Exemplary embodiments of the present invention relate to a cognitive radio system; and, more particularly, to a cognitive radio device and a master device configured for data communication and a method for data communication by the devices.
2. Description of Related Art
Various communication technologies coexist in current wireless communication systems. As a result, almost all frequency bands are allocated in wireless communication systems. Among the next-generation wireless communication systems, a Cognitive Radio (CR) system has been proposed in which, among allocated frequency bands, an empty frequency band (i.e. not in actual use) is detected, shared, and used.
In the CR system, there exists a Quiet Period (QP) on channels so that CR devices do not interfere with Incumbent User (IU) devices. The QP is used by IU devices to periodically check whether the current channel is used or not. The QP is necessary for protection of IU devices.
During the QP, CR devices suspend data transmission for the purpose of detecting whether IU devices are using channels or not, and detect whether IU devices are using channels. Therefore, the QP, though indispensable to the CR system, has a problem in that it degrades data transmission performance. Consequently, candidate channel management becomes very crucial to CR devices.